Avery's experiments identified which molecule as the genetic material responsible for transformation?

• A. Protein
• B. Carbohydrate
• C. RNA
• D. DNA

Answer: (D)

The key idea here is that a genetic material must carry heritable information that can convert one strain of bacteria into another. Avery and colleagues showed that when they took the material from the S strain and degraded different biomolecules, transformation still occurred if proteins or RNA were destroyed, but transformation did not occur when DNA was destroyed. That means the molecule responsible for carrying the heritable information—the transforming principle—was DNA. This was important because it identified DNA, not proteins, as the carrier of genetic information. The other options don’t fit because destroying those molecules did not stop transformation, while destroying DNA did.